1. Field of the Disclosure
The disclosure relates to a striped semiconductor active optical device with uniformly or non-uniformly configured gain region. In particular, the disclosure relates to a semiconductor laser diode with a gain region configured to radiate a high power output radiation with the desired near field.
2. The Related Prior Art
FIG. 1 illustrates a typical structure of semiconductor laser diode 10. The laser diode includes a substrate 12 with an elongated stripe 14—uniformly-dimensioned gain region which coextends with substrate 12 between reflectors 16 and 18, respectively. The mirrors 16′ and 18′ of the respective reflectors define the resonator. In operation, stripe 14 is traversed by current and operative to emit an optical radiation from either of the mirrors, for example, mirror 18′. The method of fabricating laser diodes is disclosed in U.S. Pat. Nos. 5,917,972, 5,978,400 and 5,985,685, respectively, all co-owned with the present application by the same assignee and fully incorporated herein by reference. The output mirror 18′, defining the near field of the output beam, is the subject to rigid requirements, i.e., its width W should not exceed a predetermined value. Otherwise, the emitted radiation would be coupled into a receiving component, such as fiber, with substantial power losses,
The ever-increasing demands for high power optical outputs are associated with increased temperature and current loads upon the stripe, which would not be of any concern if mirror 18′ was enlarged. However, as discussed above, it would be impractical. Accordingly, the stripe, experiencing high loads, is known for a relatively short useful life because elevated temperatures and high currents lead to the degradation of laser diode 10. In particular, the degradation depends on a pump current applied to gain region 14 and the heat generated in the latter. Accordingly, to combat the detrimental effect of the excessive heat, it is necessary to enlarge the area of diode 10.
The greater area may result from further elongation of laser diode 10. However, the greater length of diode 10 leads to substantial internal losses as known to an ordinary skilled worker. Accordingly, the greater the length, the greater the inner losses, the lower the effectiveness of diode 10. The diminishing effectiveness leads to greater heat generation and, by implication, shorter life cycles. The efforts directed at remedying the undesirable consequences of the increased length are translated in a cost-ineffective fabricating process.
In addition to the desired near-field of the output beam emitted in a single mode (SM) or multi-mode radiation, it is often necessary to have the desired far-field of the output beam. Otherwise, the output beam can be coupled into a waveguide such as fiber and the like, with substantial losses.
A need, therefore, exists for a high power laser diode capable of emitting the output beam with the desired near-field.
A further need exists for a high-power laser diode operative to controllably emit the output beam with the desired far-field.